1. Field of the Invention
The present invention relates to a circuit board accommodated in a casing together with a driving system of an electronic apparatus and to electrically control said driving system, to an electronic apparatus using the circuit board, and to a projection display device serving as such an electronic apparatus.
2. Description of the Related Art
Hitherto, an electronic apparatus has been used which includes a driving system, a circuit board for electrically controlling the driving system, and a casing for accommodating therein the driving system and the circuit board. As such an electronic apparatus, for example, a projection display device has been known which includes an optical system for optically processing a luminous flux emitted from a light source so as to form an optical image according to image information, a driving system including a projection lens for enlarging. and projecting the optical image onto a projection plane, a circuit board for electrically controlling the optical system and the driving system, and a casing for accommodating therein the optical system, the driving system, and the circuit board. In such a projection display device, the circuit board is often disposed above the optical system in parallel with a plane that is defined by an optical axis of the optical system.
The projection display device is widely used in multimedia presentations at conferences, academic meetings, exhibitions, etc., and hence it is necessary to improve portability in order to facilitate transportation of the device to meeting places, and a further reduction in size is demanded.
In order to meet such a demand, however, it is necessary to achieve a reduction in size of components of the optical system and to achieve a reduction in thickness of the circuit board disposed above the optical system. In particular, since the reduction in thickness of the circuit board is limited, the overall device cannot be sufficiently reduced in thickness, and a reduction in size of the device is prevented.
In addition, devices, such as a videocassette recorder and a computer, are connected to such a projection display device, and image information output therefrom is modulated by an optical modulation device constituting the optical system. This allows the projection display device to form an optical image according to the image information. More specifically, a composite signal and an RGB signal serving as image information are supplied to the optical modulation device via an optical-modulation-device driving system for driving and controlling the optical modulation device. The optical-modulation-device driving system converts, by a predetermined signal processing, image signals, such as the composite signal and the RGB signal, into signal forms suitable for image display and supplies the converted signals to a portion for driving the optical modulation device. Such an optical-modulation-device driving has been integrally formed on one circuit board as a circuit for driving the optical modulation device by input image signals.
However, the above conventional optical-modulation-device driving system formed on one circuit board encounters the following problems. That is, the optical-modulation-device driving system includes a portion that is set up according to specifications of the optical modulation device, such as the resolution (such as VGA or SVGA resolution) of the optical modulation device, and a portion that does not depend on the specifications of the optical modulation device, such as a portion for processing the composite signal and the RGB signal so as to be suitable for image display. According to the conventional optical-modulation-device driving system formed on one circuit board, a circuit board including a signal processing portion that does not depend on the specifications of the optical modulation device should be set up specifically according to the specifications of the optical modulation device of the projection display device. This is inefficient from a manufacturing viewpoint.
In addition, formation of the optical-modulation-device driving system on one circuit board increases the size of the circuit board, and this is undesirable for achieving a reduction in size of the projection display device.
Furthermore, in order to ensure a stable operation of the circuit board by preventing noise radiation, a ground section is provided on the inner peripheral surface of the casing of the projection display device, and the ground section and the circuit board are electrically connected.
More specifically, according to the conventional projection display device, the circuit board disposed horizontally above the optical system is fixed to the inner peripheral surface of the casing by a plurality of fixing screws. The fixing screws are electrically connected to the ground section, and noise generated on the circuit board is radiated at the ground section via the fixing screws to thereby achieve a stable operation of the circuit board.
However, since there is a tendency to reduce the weight, size and thickness of the overall electronic apparatus like the above conventional projection display device as described above, grounding of the circuit board by the fixing screws will restrict fixing points of the circuit board. Therefore, the electrical connection between the circuit board and the ground section via the fixing screws cannot be sufficiently effected. In addition to the electrical connection by the fixing screws, the electrical connection between the circuit board and the ground section may be achieved by providing a special connecting line on the circuit board, but this complicates the structure of the circuit board and is not desirable from the viewpoint of reducing the size of the device.
It is an object of the present invention to provide a projection display device capable of reliably reducing the thickness and size thereof without being affected by the thickness of a circuit board.
A projection display device of the present invention is intended to achieve the above object by changing a layout of a circuit board. More specifically, according to an aspect of the present invention, there is provided a projection display device including an optical system for optically processing a luminous flux emitted from a light source so as to form an optical image according to image. information; a projection lens for enlarging and projecting an image formed by the optical system onto a projection plane; a circuit board for controlling the device; and a casing for substantially covering the optical system, the projection lens, and the circuit board in entirety, characterized in that the circuit board is substantially perpendicular to a plane defined by optical axes of the optical system, and is disposed longitudinally on an outside of the plane defined in the optical system.
In the projection display device of the present invention, when the plane defined by the optical axes of the optical system is set horizontally, for example, the circuit board is allowed to stand aside the optical system. Therefore, by designing the circuit board so as to have a small size, the entire thickness of the projection display device can be reduced because the circuit board is not disposed above the optical system. Therefore, unlike the conventional projection display device in which a circuit board is disposed above an optical system, the thickness of the entire device can be reliably reduced regardless of the thickness of the circuit board, whereby a reduction in size of the device is sufficiently facilitated.
In addition, in the projection display device of the present invention, the circuit board may be disposed in such a manner that one surface of the circuit board closely oppose an inner surface of the casing, and a guard member may be provided between the circuit board and the casing so as to prevent interference therebetween.
That is, the guard member is provided between the circuit board and the casing, so that interference between the casing and the circuit board is prevented. In particular, the circuit board can be effectively prevented from being damaged. In addition, this allows the casing to be easily mounted, whereby efficiency of assembly work can be improved.
In the projection display device of the present invention, the guard member may include a metal planar section for covering a predetermined area of the circuit board.
In this case, the circuit board is protected from external noise, and malfunction of the circuit is prevented.
Furthermore, in the projection display device of the present invention, the casing may be provided with a supporting section for supporting the circuit board, whereby the mounting operation of the circuit board is facilitated.
In addition, in the projection display device of the present invention, a power-supply circuit board may be provided separately from the circuit board, and an electric power for driving a control circuit on the circuit board may be produced by a power-supply circuit on the power-supply circuit board.
In this case, the electric power for driving the control circuit formed on the circuit board is produced on the power-supply circuit board provided separately from the circuit board, so that the control circuit becomes resistant to received noise, as compared with a case where the power supply circuit is formed on the circuit board. Therefore, it becomes difficult for the malfunction of the control circuit to occur, whereby reliability is increased.
It is another object of the present invention to provide a projection display device including a light source, an optical system for optically processing a luminous flux emitted from the light source so as to form an optical image according to image information, and a projection lens for enlarging and projecting an image formed by the optical system onto a projection plane which can achieve commonality of components, improve productivity, and contribute to reduced size of the device.
To achieve the above object, according to another aspect of the present invention, there is provided a projection display device including an optical system for optically processing a luminous flux emitted from a light source so as to form an optical image according to image information; a projection lens for enlarging and projecting an image formed by the optical system onto a projection plane, characterized in that an optical-modulation-device driving system for driving and controlling an optical modulation device constituting the optical system is provided, and that the optical-modulation-device driving system is divided into an individual-setting section set according to specifications of the optical modulation device and a common-setting section set in common without depending on the specifications of the optical modulation device.
The above individual-setting section includes, for example, a phase expansion circuit for expanding an image signal supplied as serial data according to the resolution of the optical modulation device. In addition, the common-setting section includes, for example, a look-up table (LUT) for outputting a drive controlling signal for allowing the optical modulation device to display a predetermined color according to the input image signal, and a CPU for setting and controlling table information for the LUT.
In addition, various types of elements, such as an active-matrix driving liquid crystal element, an electro-luminescent element, and a plasma display element may be employed as the above optical modulation element. Furthermore, the optical-modulation-device driving system may drive and control simultaneously a plurality of optical modulation display devices, like a three-sheet projection display device for modulating each color of red (R), green (G), and blue (B).
According to the present invention, the optical-modulation-device driving system is divided into the individual-setting section and the common-setting section, so that only the individual-setting section may be changed even if the optical modulation device in the projection display device has different specifications, whereby management of components can be rationalized and productivity of the projection display device can be improved. In addition, the optical-modulation-device driving system is divided into the individual-setting section and the common-setting section, so that versatility of arrangement of the optical-modulation-device driving system in the projection display device is increased, thereby contributing to reduced size of the device.
In the projection display device, the individual-setting section and the common-setting section may be formed on two separate circuit boards, respectively, and the circuit boards may be stacked.
That is, the circuit board on which the individual-setting section is formed and the circuit board on which the common-setting section is formed are stacked, so that electrical connection between the two circuit boards can be easily established, whereby the productivity of the device can be further improved. In addition, two circuit boards are stacked, so that it is possible to efficiently cool the optical-modulation-device driving system by introducing cooling air into a space formed between the two circuit boards.
In addition, the individual-setting section may be provided with an information carrier circuit for carrying setting information for the optical modulation device, and the common-setting section may be provided with a correction circuit for obtaining setting information for the optical modulation device from the information carrier circuit, correcting the input image information based on the setting information, and outputting the corrected information.
As the information carrier circuit, an information carrier circuit including switching elements selectable between Low and High, an information carrier circuit including a non-volatile storage unit for recording setting information for the optical modulation device, and an information carrier circuit which may consist of the switching elements and the storage unit may be employed.
As the correction circuit, a correction circuit may be employed which includes an LUT for outputting a drive controlling signal for allowing the optical modulation device to display a predetermined color based on the input image signal, and a CPU for setting and controlling table information of the LUT based on the setting information obtained from the information carrier circuit.
That is, the individual-setting section includes the information carrier circuit, so that the setting information carried by the information carrier circuit can be obtained by the correction circuit of the common-setting section so as to correct the image signal. Therefore, even if the optical modulation device has different characteristics, it is possible to suitably ensure color reproducibility of a projected image of the projection display device.
In addition, when the information carrier circuit includes selectable switching elements, the information carrier circuit can carry relatively simple information, such as a resolution of the optical modulation device. More specifically, when the information carrier circuit carries setting information about the resolution, the resolution can be recognized by the following combinations of the Low-and-High selectable switching elements.
Furthermore, when the information carrier circuit includes a non-volatile storage unit, the information carrier circuit can carry complicated setting information, such as an applied voltage and light transmission characteristics of the optical modulation device, and setting information for a plurality of optical modulation devices can be recorded in one storage unit. As the non-volatile storage unit, an Erasable Programmable Read Only Memory (EPROM), or an Electrically Erasable Programmable Read Only Memory (E2PROM) may be employed. In brief, various types of storage units may be employed so long as they are information-writable units and they do not lose recorded information even if the power of the projection display device is shut off.
It is a further object of the present invention to provide a circuit board accommodated in a casing together with a driving system of an electronic apparatus so as to electrically control the driving system, and an electronic apparatus using the circuit board which can prevent generation and intrusion of noise into the circuit board without depending on a layout direction, and secure a stable circuit operation.
According to a further aspect of the present invention, there is provided a circuit board accommodated in a casing together with a driving system of an electronic apparatus so as to electrically control the driving system, characterized in that the casing is provided with a ground section for preventing radiation of noise produced inside the casing and for preventing intrusion of external noise into the casing, and that the circuit board includes an electrical conducting portion provided on the outer peripheral end of the circuit board, and electrically connected to the ground section.
An electrical conducting portion provided along the entire outer periphery of the circuit board, an electrical conducting portion provided on a part of an outer peripheral end, and electrical conducting portions provided at a plurality of points may be employed as the above-described electrical conducting portion.
According to the present invention, the electrical conducting portion is provided on the outer peripheral end of the circuit board. Therefore, when the electrical conducting portion is brought into contact with the ground section provided inside the casing, electrical connection therebetween can be established, whereby generation and intrusion of noise into the circuit board is prevented without depending on a layout direction of the circuit board, and a stable circuit operation is ensured.
In the circuit board, an electrical conducting portion composed of a metal conducting portion that is formed on at least a part of the outer peripheral end of the circuit board may be preferably employed as the electrical conducting portion. More specifically, the metal conducting portion can be formed by forming a metal plated layer on the outer peripheral end of the circuit board, or by covering the outer peripheral end of the circuit board with a metal plate.
For example, the metal plated layer can be formed on the metal conducting portion as follows. First, a long through-hole having the metal plated inner peripheral surface is formed in a printed wiring circuit board. Then, the circuit board is cut along the length of the through-hole to divide the circuit board, whereby a metal plated layer is exposed to the outer peripheral end of the circuit board to form the metal conducting portion.
When the metal conducting portion is formed of a metal plated layer, in forming the printed wiring on the circuit board, the electrical conducting portion can be formed simultaneously in a step for forming the through-hole, whereby manufacturing of the above circuit board can be facilitated. In addition, when the electrical conducting portion is formed of a metal plate covering the outer peripheral end of the circuit board, the electrical conducting portion can be formed after preparing the circuit board, and the electrical conducting portion can be formed successively along the outer peripheral end of the circuit board.
According to a still further aspect of the present invention, there is provided an electronic apparatus including a driving system; a circuit board for electrically controlling the driving system; and a casing for accommodating therein the driving system and the circuit board, characterized in that the casing is provided with a ground section for preventing radiation of noise produced inside the casing and for preventing intrusion of external noise into the casing, and a holding member electrically connected to the ground section and holding the circuit board, that the circuit board is provided with an electrical conducting portion formed on an outer peripheral end of the circuit board and electrically connected to the ground section, and that the electrical conducting portion and the ground section are electrically connected via the holding member.
According to the present invention, the ground section of the casing and the electrical conducting portion of the circuit board are electrically connected via the holding member, so that it is not necessary to provide a special connecting line, etc. on the circuit board, and the circuit board and the ground section can be easily electrically connected.
In the electronic apparatus, a holding member composed of a metal member engaging with the circuit board may be employed as the above-described holding member, but a holding member may preferably be composed of an elastic member that is deformed according to a contact condition of the circuit board. More specifically, a strip holding member composed of a spongy elastic member and a conductive sheet provided on an outer peripheral surface of the elastic member may be employed as the holding member.
That is, the holding member is composed of the elastic member and the conductive sheet provided on the outer peripheral surface of the elastic member, so that the holding member is deformed according to the contact condition of the circuit board, whereby electrical connection between the ground section and the electrical conducting portion can be reliably established via the conductive sheet of the holding member.
A ground section having a metal plate attached to the inside of the casing may be employed as the above-described ground section, but a ground section composed of a shield plated layer formed on an inner surface of the casing may preferably be employed.
That is, the ground section is composed of the shield plated layer formed on the inner surface of the casing, so that the ground section can be easily formed in the outer casing, the ground section can be simplified, and the inner structure of the electronic apparatus can be simplified, whereby the size of the electronic apparatus can be further reduced.